1. Field of the Invention
This invention relates to an image processing apparatus, method and computer-executable program product for converting the format of data for specific image data, and in particular, for converting the order of pixel data supplied in a predetermined format.
2. Description of the Related Art
A compression method with Discrete Cosine Transform (DCT), such as JPEG, has been used for compressing digital image data. Using DCT compression technique, it is necessary to divide image data into block form image data of a predetermined size, as shown in FIG. 1. When using the JPEG method, image data is divided into blocks of 8 pixels.times.8 pixels. Therefore, it is usually necessary to provide a buffer memory which is capable of storing image data of at least 8 lines to perform DCT in real time. Further, when raster image data is compressed in real time, it is necessary to use another buffer memory which hold the image data from image processor while the raster image data is divided into blocks.
However, conventionally, it is not possible to perform data format conversion efficiently. In particular, in a case where the raster image data is composed of plural components, the data format conversion becomes very inefficient.